1. Mechanical Aspects of Corrosion
Dr. Abdolali Fayyaz
Assistant Professor
Department of Materials Engineering,
Science and Research Branch, Islamic Azad University, Tehran,Iran
Email: abdolali.fayyaz@gmail.com ; a.fayyaz@srbiau.ac.ir
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2. Dr. Abdolali Fayyaz
B. Eng (Tehran University, Iran)
MSc (Sharif University of Technology, Iran)
Ph.D (National University of Malaysia, Malaysia)
Assistant Professor
Department of Materials Engineering, Islamic Azad University,
Sciences and Research Branch, Tehran ,I.R.Iran.
E-mail: a.fayyaz@srbiau.ac.ir , E-mail: abdolali.fayyaz@gmail.com
Research interest:
- Materials Science and Manufacture Engineering
- Powder Metallurgy and Particulate Materials Processing
- Casting and Solidification
- Advance Manufacturing Process
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3. References
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1Mechanical Metallurgy, G E Dieter, Mc Graw Hill Book
Company, Third Edition, 1988.
2Deformation and Fracture Mechanics of Engineering Materials,
Richard W. Hertzberg, Richard P. Vinci, Jason L. Hertzberg, Wiley
John Wiley & Sons, Inc, Fifth Edition, 2013.
3Stress Corrosion Cracking: Theory and Practice, V
. S Raja, T.
Shoji Woodhead Publishing; 1st edition, 2011.
4Corrosion fatigue: mechanics, metallurgy, electrochemistry and
engineering, T. W. Crooker and B. N. Leis, ASTM, 1983.
5 Fundamentals of Hydrogen Embrittlement, M. Nagumo,
Springer; 1st edition, 2016.
4. Course Description
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This course provides a critical review of the state of knowledge
and understanding of the process of mechanical aspects of
corrosion. The theoretical background of fracture mechanics is
also reviewed.
In particular, this course is intended to provide an understanding
of the physical and mechanical mechanism that relate to
environment-assisted cracking and to indicate how these
processes combine to produce the phenomena observed in
practical situations.
An essential aims of this course are to understanding interaction
between static or dynamic stress and the environment. The
environmentally induced cracking (EIC) typically include stress
corrosion cracking (SCC), corrosion fatigue cracking (CFC),
hydrogen embrittlement (HE), and liquid-metal embrittlement
(LME).
5. Components of Your Grade
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1) Exams (final: 50%)
2) Seminar and Presentation (35%)
3) Attendance (15%)
Please be on time (Being late disrupts the instructor and other students).
Please participate in class discussions.
Remarks: The weight of each grade component may change up to 5% depending on the student’s
achievement.
6. Mechanical Aspects of Corrosion SeminarTopics
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Mechanical Aspects of Corrosion (SCC or CFC or HE)of
Steel and steel alloys
Stainless Steel (differentgrades)
Aluminum and aluminum alloys
Copper and copper alloys
Titanium and titanium alloys
Magnesium and magnesium alloys
Superalloys
Polymer
Ceramics
Or
Some components and parts such as turbine rotor, oil and gaspipeline,
boiler, aerospace vehicles, ….
Presentation time (Min.): 20 minutes
Deadline for submission: one month before the end of semester
9. Corrosion
Corrosion is a natural process that converts a refined metal and
alloys into a more chemically stable form such as oxide,
hydroxide, carbonate or sulfide. It is the gradual destruction of
metal and alloys by chemical and/or electrochemical reaction
with their environment.
Since the 1950s several countries considered the economic
consequences of corrosion. Studies conducted during this time
indicated that the cost of corrosion to society was significant.
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10. The global cost of corrosion is estimated to be US$2,505 billion,
which is equivalent to 3.4% of the global GDP (2013). In
addition, these costs typically do not include individual safety or
environmental consequences.
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11. Perhaps most dangerous of all is corrosion that occurs in major industrial
plants, such as electrical power plants or chemical processing
plants. Plant shutdowns can and do occur as a result of corrosion. This is
just one of its many direct and indirect consequences. Some consequences
are economic, and cause the following:
Replacement of corroded equipment
Overdesign to allow for corrosion
Preventive maintenance, for example, painting
Shutdown of equipment due to corrosion failure
Contamination of a product
Loss of efficiency—such as when overdesign and corrosion products
decrease the heat-transfer rate in heat exchangers
Loss of valuable product, for example, from a container that has
corroded through
Inability to use otherwise desirable materials
Damage of equipment adjacent to that in which corrosion failure occurs
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Few Disasters Caused By Corrosion
Genoa, Italy Bridge Collapse
In August of 2018, a bridge collapsed in Italy
resulting in the death of 43 people. The bridge was
only 51 years old, and was frequently used by local
citizens. The steel cables supporting the bridge failed
due to damage from corrosion.
Sinking of the Erika
In December of 1999, a Maltese tanker broke in two
while traveling near the coast of Brittany France.
Nearly 19,800 tons of oil were spilled.
There were multiple parts of the ship that had failed
due to corrosion, and the final straw that broke it apart
was severe weather. There were immense economic
and environmental consequences for the region.
Bhopal, India Incident
In December of 1984, one of the world's largest
industrial disasters occurred, resulting in the death of
nearly 8,000 people. Corrosion caused toxic gas
(phosgene, monomethyl amine (MMA), methyl
isocynate (MIC) and the pesticide carbaryl, known as
Sevin) from a pesticide plant to leak into the atmosphere.
13. Still other consequences are social. These can involve the following
issues:
Safety, for example, sudden failure can cause fire, explosion, release
of toxic product, and construction collapse
Health, for example, pollution due to escaping product from corroded
equipment or due to a corrosion product itself
Depletion of natural resources, including metals and the fuels used to
manufacture them
Appearance as when corroded material is unpleasing to the eye
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14. Several studies separated the total corrosion costs into two parts:
1.The portion of the total corrosion cost that could be avoided if better
corrosion control practices were used, and
2.Costs where savings required new and advanced technology
(currently unavoidable costs).
The original study identified ten elements of the cost of corrosion:
Replacement of equipment or buildings
Loss of product
Maintenance and repair
Excess capacity
Redundant equipment
Corrosion control
Technical support
Design
Insurance
Parts and equipment inventory
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15. Environmental stress cracking (ESC) is a costly form of premature
fracture of metal structures touching all corners of life in the world
and industrially developed nations and it is very costly in terms of
public safety arid property damage. There
is hardly a metal known that does not have alloy systems
susceptible to environmental cracking of some sort, and this is the
case for certain polymeric materials, as well.
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Why investigation about
Environment-Assisted Cracking
is
Important?
16. Under tensile stress, and in a suitable environment, some metals
and alloys crack . . . usually, SCC noted by absence of
significant surface attack . . . occurs in “ductile” materials.
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A structure that has SCC sensitivity, if subjected to stresses and
then exposed to a corrosive environment, may initiate cracks and
crack growth well below the yield strength of the metal.
While rare, Stress Corrosion Cracking (SCC) offers very little in
terms of visual hallmarks, material deformation, or other
common detection methods. This means that metal which
otherwise looks shiny and in excellent condition can suddenly
catastrophically fail with little to no warning.
17. 1965 (March 4) A 32-inch gas transmission pipeline, north of Natchitoches, Louisiana,
belonging to the Tennessee Gas Pipeline exploded and burned from Stress corrosion
cracking (SCC) on March 4, killing 17 people. At least 9 others were injured, and 7
homes 450 feet from the rupture were destroyed. The same pipeline had also had an
explosion on May 9, 1955, just 930 feet (280 m) from the 1965 failure.
Few Disasters Caused By Environment-Assisted Cracking
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18. On December 15, 1967, the Silver Bridge collapsed under the weight of rush-hour
traffic, resulting in the deaths of 46 people. Two of the victims were never found.
Investigation of the wreckage pointed to the cause of the collapse being the failure
of a single eye bar in a suspension chain, due to a small defect 0.1 inches (2.5 mm)
deep. Analysis showed that the bridge was carrying much heavier loads than it had
originally been designed for and had been poorly maintained and also appear
corrosion in some part of bridge.
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20. Roof Collapses on Swimming Pool in Switzerland on 9 May, 1985
-, killing 12 people
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21. In the Netherlands, for example, a ceiling collapsed during the night of 8/9 June
2001 at a pool in Stenwijk. It was discovered the next morning by a party of
visiting swimmers; fortunately there were no casualties. The pool had been open
only nine years, and chlorine was again used to disinfect the water of the pool.
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22. In literature, several types of environmentally
induced cracking have been reported.
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1. Stress corrosion cracking (SCC)
2. Corrosion fatigue cracking (CFC)
3. Hydrogen induced cracking (HIC)
or hydrogen embrittlement (HE)
4. Liquid metal embrittlement (LME)
24. pieces due to stress, at
Fracture: separation of a body into
temperatures below the melting point.
Steps in fracture:
1. Crack formation / Crack nucleation
2. Crack propagation / Crack growth
Fracture
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25. Depending on the ability of material to undergo plastic deformation
before the fracture two fracture modes can be defined
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Ductile or Brittle
Ductile fracture - most metals (not too cold):
Extensive plastic deformation ahead of crack
Crack is “stable”: resists further extension unless applied stress is
increased
Brittle fracture - ceramics, ice, cold metals:
Relatively little plastic deformation
Crack is “unstable”: propagates rapidly without increase in applied
stress.
**Ductile fracture is preferred in most applications**
26. Ductile materials - extensive plastic deformation and energy
absorption (toughness) before fracture.
Brittle materials - little plastic deformation and low energy
absorption before fracture.
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27. A. Very ductile, soft metals (e.g. Pb, Au) at room
temperature, other metals, polymers, glasses at high temperature.
B. Moderately ductile fracture, typical for ductile metals
C. Brittle fracture, cold metals, ceramics.
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A B C
28. Ductile Fracture (Dislocation
Cup-and-cone fracture inAl
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Tensile failure
Spherical dimples correspond to microvoids
that initiate crack formation.
Mediated)
(a)Necking
(b) Formation of microvoids
(c) Coalescence of microvoids
to form a crack
(d)Crack propagation by shear
deformation
(e) Fracture
Shear failure
29. 1. No appreciable plastic deformation
2. Crack propagation is very fast
3. Crack propagates nearly perpendicular to the direction
of the applied stress
4. Crack often propagates by cleavage – breaking of
atomic bonds along specific crystallographic planes
(cleavage planes).
Brittle fracture in a mild steel
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